Straightforward trunking system



sept. 21,1926. 1,600,556

W. H. MATTHIES `STRAIGHTFORWARD TRUNKING SYSTM Filed July 8. 1925 EQU oFFlcE @(2. nim* OFF'lCE 2 @uns a" "5.

VV/7//' /77 H Maf/Wes ,b /wy Patented Sept. 21, 1926.

15ans-56A i UNITED STATES i PATENTS jfilari- 2151. y

WILLIAM H. MATTHIES. OP HACKENsACK, NEW yJERSEY; AssIc-:p-NOE To WESTERN ELECTRIC COMPANY, INCORPORATED, or NEW YORK, N. Y., A CORPORATION OP NEW YORK.

ysTRAIGfIITEORWARn Application filed July s,

This invention relates to telephone systems and more particularly to an improvement in trnnking arrangements for straightforward trunking systems. y

An object of thisinvention is to provide a simplified .andinexpensive arrangement for trunking at telephonev oiiices whereby a number of smaller otlices, instead of as heretofore having individual trunks leading to a distant larger oflice, 7may bek provided with trunks leading to an adjacent intermediate or centrally located Office and having this intermediate office Ain turn connected to trunks leading tothe distant larger oflice.A

In this arrangemenuthe number of trunks out going to the larger office will be less than the total number of trunks incoming tothe intermediate oiice. The advantage of such an arrangement is particularly evident when these ofiices are located in large cities where underground cable installations between the offices areextremely costly. The longer and therefore more expensive trunk lines between an .intermediate and distant oflice will rbe few; that is, only a suiicient number'of such trunks will be provided to care for the totalv traiiic that islikely to be anticipated between all the smaller otlices and the distant oiice. A considerable saving is thereby effected in the interest chargesnon investments in cables and a higher efficiency is obtained in the use of the cables provided.

Another object of the invention is to provide'in a simplified trunking arrangement of this'type an all trunks busy arrangement requiring the minimum amount of apparatus individual to the incoming Vtrunks and a greatly simplified equipment common to the outgoing trunks.

To attain these and other objects of the invention. as will hereinafter appear, there is provided Yat the'intermediate ofiice a trunk hunting switch for each trunk line incoming Y from the smallerofiices and automatic cir-1 cuit arrangements wherebyl the moment a trunk is seized by an voperator at a smaller office, the corresponding switch at the intermediate oiiicewill be actuated to hunt for and connect said .trunk with an idle trunk Vleading to the distant larger office. n

'A feature ofthe invention is the provision in a systemV of the above type .of means whereby va busy test condition will be prepared for Vall the trunks incoming tothe intrunk or trunks seized after. v,trunks are engaged. Y

TRUNKING SYSTEM. i

1925. Serial No. 42,121.

termediate `oflice from thesmaller yoliices when all trunks outgoing therefrom to the larger oiiice are engaged; the arrangement f boing such that when all suchv trunks are busy and vwhen an operator yat a smaller oftice attempts to establish a connection by engaging a trunk leading;rr to the intermediate oflice' a busy condition will be applied to that trunk as an indication that all v outgoing trunks are engaged. y Y `Another feature residesin means whereby :said prepared condition is in tlieform of ay tone on the tip conductor of the' incoming yall outgoing y Another feature of this invention resides kin the provision of means whereby after an all outgoing trunk busy condition is established `and another incoming trunk is seized the corresponding switch is actuated to hunt lfor an i'dle outgoing trunk and if the incoming' trunk is heldafter one'ormore of the outgoing trunks becomeidle this switch continues to hunt for an idle outgoing trunk yand when found connects'v the corresponding incomingtrunk therewith. Y l In the accompanying drawing is illustrated a straight-forwardy trunking systemA with the'circuit arrangement for one of a plurality fof incomingtrunks4 from each of .two -i smaller oiiices and their Corresponding trunk hunting switches at an intermediatel oiiice, and also two outof a plurality of trunks outgoing. to a distant oilice. The f busy test equipment commonvto 'all of these incoming and outgoing trunksis also illustratedA inthe drawing. y i

Refer-ring now. specifically to the-details of the system illustrated in this drawing, the

to an idlet-runksuchfas l1 or .12 of a group.

ot trunks outgoing to a distant ollice. vTrunks such as 11 and 12 are multipled to other trunk hunting switchesY such as 10, each of which may be associated with a trunk such vas 3 leading to and terminating in jacks such The Iswitchl and its associated relay cir- ,cuit arrangement 16 is identical with the switch V and its relay and ycircuit arrangement and it should be understood that the outgoing trunks 11 and 12 may be multipled not only to switch 15 but also to other switches associated with other trunks such as G'leadingto olice 2. While only two smaller oflicesjhaye been illustrated, alarger numbery of such oii'ces may be similarly equipped and connected through the intermediate oilice= and the outgoing trunksto the distant largeroliice. Y

Toset tort-h the operationV of this trunking arrangement, it will be explainedin the following` detailed description ot the invention, first, how the system operates when a'call from othce 1 is to be extended'over trunk 3 through theinterinediate olice by means of switch lOand its associated relay and circuit arrangement to a distant larger otlice, and second, how the busy test arrangement common to all they incoming trunks at thisrinterinediate oiiice operates when all of theoutgoing trunks are engaged and an operator at oiiice 1 attempts to,l establish a connection. Y It' it is assumed then thatan'operator at a position in'otlice 1 inserts the calling plug of a lcord circuit into jack'2,'tor example, itis well known in the art that the tip terminal of jack' 2 will be connected to ground and a circuit will therefore be established as tollows: battery, upper inake-before-'break contact of relay 20,; upper winding of relay 21, tip conductor'o'f trunk line' 3, tip terminal of jack 2 to ground vat the operators cord circuit. This causes the operation of relay 21 which'in attracting itsv armature' closes a circuit for relayy 22 as follows: battery, ar-

' mature and'frontcontact ovfrelay 2.1, lower make-betore-break contacts.' of relay 20, upper winding of relay 22 to ground. "This causes the operation'of relay 2-2 which in attracting its vupper 'armatures opens thel tip and ringconductors to the switch 10`to prevent interference with a possiblefother con-A nection over the outgoing trunks'terminatingl at this switch. The operation otY relay' 22'alsoA closesv a circuit for relay 20 as fol-i lows: battery, armature and front Contact of relay 21', lowerinner armature and front" contact of relay 22, win'tding'vof relay 20 to,r lground.' Bela;7 2() in'operatin'g closes la. lockring' brushes 27 and 28 of Aswitch 10.

ing circuit for itselr" through its low-er middle armature and front contact to the bat tery at the armature and front contact oi`l relay 21 and also connects at'its upperarmature and front contact and lower'inner armature and front contact the tip and ring leads from trunk line 3 to contacts ot relay 22. The operation of relay 2O opens the circuit 'for the Iupper winding of relay 22 but the circuit for the lower winding of this relay 22 is `now extended from the .battery at the varmature and front contact of relay 21, through this winding, the lower, outer armature and front Contact of relay 22 to the hunting brush 25V of switch 10. It4 should be noted that a parallel path is also established to ythe hunting-brush for the stepping magnet26 from the battery at the Varmature and front contact of relay y21, vthrough the lower outer armature and front contact of relay 22; It the switch 10is resting with its brushes on a busy outgoing trunk, ground from the sleeve leadv of this trunk through the Vhunting brush 25 is supplied for maintaining. relay 22 energized. The same ground causes the stepping magnet 26 to operate and in operating interrupt its own circuit so that it will release and ystep the brushes'ot switch 10 on to the'next trunk terminals.- ln case the next trunk is also busy4 and consequently has its'sleeve lead grounded, the switch operates again and this action is repeated until the brushes finally come to rest on the terminal of an idle'trun'k. The hunting brush25 is so constructed as not to open the circuit to the sleeve terminals when stepping 1from one terminal to another and the circuity for thelower winding yof relay 22 istherefore maintained until the idle trunk is reached. WhenV theV switch 1() therefore linal-ly comes to'rest on idle eutgoing trunk, the sleeve circuit `through the lower winding or relay 22 is broken sothat this relay in releasing now completeslthe connection otthetipand ring conductors from' the trunk line 3 through to the tip and lt should also be noted that a-busy condition is now established onthe sleeve terminal of trunk from ground at the lower outer armature and front contact of relay 20 through the lower outerV armature and back contact of relay 22 through brush 25 so that the selected trunk willvnow test busy to other switches to which itsrterininals are mul-ti-` pled. Vlien relay 2.2 releases, the condition willtherefore' besuch that relay 21l will be maintained energized by jhaving its ytwo windings included in the tip and ring leads of'this trunk Vline 3, and consequently, relay 20 will also be held-lockedby virtue of the operation ofrelay 21. Y

It" it is now assumed that all oft thetrunks such as 11 and 12 jleading to theV distant larger otlice are engagethit will be seen that on every seizure of a trunk to this oiice by switches such as 10 or 15, the associated sleeve terminals of these switches will cause the operation of the corresponding relays such as 29 and 30; that is, tor example, relay 29 will be operated when trunk 11'is engaged by a circuit 'from battery, winding ot relay 29, through a hunting brush such as 25, lower outer armature and back contact of a relay such as 22, lower outer armature and front contact ot a relay such as 2() to ground; while when trunk 12 is engaged relay 30 will be operated over a similar circuit through an associated sleeve terminal and hunting brush to ground at a relay such as 20. In case thereiiore that all of the trunks to the larger oiiice are engaged, all of the relays such as 29 'and 30 will be operated and through a series circuit will cause the operation of relay 31. This circuit may be traced as 'follows; battery through the winding ot' relay 31 over a circuit through the armatures and front contacts of relays such as 30, through the armature and front contact ot relay 29 to ground. Relay 31 in operating closes a connection from ground through an interrupter 32, the armature and front contact of this relay 31, and therefrom through the circuit of all relays such as 22 of the relay and circuit arrangements associated with switches such as 10 or 15 or other switches at the intermediate office, through condensers such as 33 of the relay Aarrangement associated with the switch 10 or condenser 34 of the relay arrangement associated with switch 15 and corresponding condensers of other relay and circuit arrangements associated with other switches. That is, if thereV are twenty outgoing trunks to the larger oihce, twenty circuits are completed from the ground at iiiterrupter 32 through the twenty condensers such as 33 and 34: ot twenty switches such as 10 and 15.

It now an operator, for example in oiiice 1, attempts to establish a connection to the distant larger oiiice by inserting a calling plug in a j ack such as 1, the functions hereinbefore described for the operation of relays such as 21, 22 and 20 and stepping magnet 26, of the relay arrangement and switch associated with the trunk selected, will take place. That is, the switch such as 10 would begin hunting for an idle trunk. Upon `the operation of a relay such as 22, a circuit will be established from battery through the upper outer armature and front contact of a relay such as 20, and winding ot a relay fsuch as 21, tip conductor of a trunk such as 3, tip terminal of a jack such as 1 to the busy test winding of the operators telephone set of the cord used, as is well known in the art. It will be noted that the circuit from battery through a condenser such as 33 through the interrupter 32 to` ground will alternately charge and discharge the condenser 33 at the rate of interruptionsand consequently a tone termediate oiiice to the distant larger oi'ic'e are available, the voperator will disconnect lier cord from the' jack such as 1. This disconnection vreleases/the relays such as 21, 2O and 22 and the magnet such ras 26 so that the Vcorresponding switch will stop its hunting movement. It should be noted that in case an outgoing trunk becomes idle while the operator is still connected to a jack such as 1 or 2 the corresponding switch will step on I the terminals oic this idle trunk and relay 22 will release and remove the busy tone from the corresponding incoming trunk. The operator may under these circumstances remain connected and extendthe connection l further.

It the operator at the position at which jack 1 is located attempts to connect with trunk line 3 and this trunk is already engaged by the operator at the positionat 'f which jack 2 is locatedas through any other jack multipled toA trunk line 3, she will nat-V urally find that it is engaged by listening to the conversation over the trunk carried on by lthe connected subscriber.

What is claimed is:

1. In a trunk system comprising a large number of jack terminals, corresponding switches and a comparatively smaller number of trunks accessible thereby, means for establishing a busy condition for such jack terminals as are notused in the connections responsive to the engagement of Aall of said trunks, and means for connecting said busy condition means to the terminals of any idle jack responsive to it being seized while all trunks are engaged.

2. In a straightforward trunking system, groups ot trunks incoming from diiierent oiiices, an individual switch 'for each trunk at an intermediate otlice, a single group ot trunks outgoing from` said switches, smaller in number than the total number Vof incom ing trunks and switches, means associated with each incoming trunk and its switch responsivc to the seizing of the trunk tor'operating said switch to hunt for an idle outgoing trunk, means responsive when all outgoing trunks are engaged for establishing a busy condition for all incoming trunks not in use and means individual to each incoming trunk each responsive to the seizing of the corresponding ytrunk after the busy condition has been established for indicatsuch busy condition.

3. In a trunking system, groups of trunks an incon'iing trunk, a smaller number of trunks available to said switches and outgoing to a distant office, means associated with each incoming trunk for operating the `corresponding switch to hunt for and conneet said incoming trunk with an idle out going trunk, and means for transmitting a busy signal over the incoming trunk the corresponding switch of which is hunting` for an idle outgoing trunk if all the outgoing trunks are engaged. l

4. In a trunking system, groups ot trunks incoming from different oiiices to an intermediate centrally located onmice, switches at the intermediate oiliceone tor each incoming trunk, a smaller number lof trunks available to said switches and outgoing to a distant office, means associated With each incoming trunk for operating thev correspond ing switch to hunt torand connect said incoming trunk with an idle outgoing trunk, means for transmitting a busy signal over the incoming trunk the corresponding switch of which is hunting for anidle outgoing trunk if all the outgoing trunks are engaged, and means for discontinuing the transmission vozt the busy signal nVer said in- In a trunking system, incoming trunks,

a smaller number of outgoing trunks, switchingmeans associated With each incoming trunk and responsive to the seizing thereof ttor limiting tor and connecting the seized incoming trunk Withan idle *outgoing` trunk, means for transmitting a busy signal to any incoming trunk when seized resoonsive When all of said outgoing trunks are engaged by other incoming trunks, means Yfor discontinuing the' busy signal to said seized incoming trunk if'any et the outgoing trunks Vbecome idle While said incoming trunk is still seized and means 'for Aeentinuing the trunk limiting movement of tl corresponding switching means of said seized incoming trunk after the busy signal is discontinued and until the idle Outgoing trunk is found. I

ln witness whereof, I hereuntosubscribe my naine this 7th day of rJuly A. D., 1925.

WinnniM H. MATTHIES.

DISCLAIMER.

1,600,556.-Wz'tttam E. Matthies, Hackensack, N. J. STRAIGHTFORWARD THINKING SYs'rnM. Patent dated September 21, 1926. Disclaimer filed September 29, 1928, by the assignee, -l/Vestern Electric 00m/pany, Incorporated.

Hereby enters this disclaimer to the said claim of said Letters Patent which is in the following Words, to Wit:

5. In a trunking system, incoming trunks, a smaller number of outgoing trunks, switching means associated With each incoming trunk and responsive to the seizing thereof for hunting for and connecting the seized incoming trunk with an idle outgoing trunk, means for transmitting a busy signal to any incoming trunk when seized responsive when all of said outgoing trunks are engaged by other incoming trunks, means for discontinuing the busy signal to said seized incoming trunk if any of the outgoing trunks become idle While said incoming trunk is still seized and means for continuing the trunk hunting movement of the corresponding switching meansffofsaid seized incoming trunk after the busy signal is discontinued and until the idle outgoing trunk is found.

[Ojjtez'at Gazette October 23, 1928.] 

